Hey, thanks for the feedback!
Yeah, that is something that I've been meaning to fix, and I actually go slightly into why that occurs in my post-mortem.
Essentially, the "voxel system" I currently have isn't actually a voxel system atm. It's more just a collection of "subvoxel" cube objects that are parented to a "main voxel" object. What this also means is that when physics calculations are being done on the grid, such as when moving it around as an item, it starts lagging hard since the game now has to keep track of hundreds, if not thousands of physics objects.
While I do plan on fixing this later by means of an actual voxel-based system and dynamically-generated meshes, it's probably going to be a while until I get to it :/